This invention relates to an improved audio/videodisc synchronizer for presenting still frame audio/visual presentations.
There currently exist several methods of presenting still frame audio/visual displays. For example, a slide show or film strip presentation utilizes an audio tone to advance the projector. This normally is a 50 Hertz tone recorded in the audio track and filtered out during playback. The visual frames must be imaged on the film in correct presentation order for a film strip. For a slide show, typical carousels have a limited number of slides which they may hold. This number is generally less than 140 slides.
It currently is also possible to compress a limited amount of audio onto a video frame. By current methods, this consists of about thirty seconds per frame. The audio is not of a quality acceptable, however, to most critical professionals and is further limited when going to stereo response. More importantly, "remastering" to add, delete, or modify audio or video is expensive and time consuming and video frames and audio must be recorded in sequential order.
Another currently available alternative is the utilization of a video tape source. A video tape source, however, has limited still frame capabilities and is not very stable in still frame mode. Consequently, a still frame is continuously recorded onto a free-running video tape. This allows for increased quality and duration of audio, but the video tape does not provide a stable image on commercial or industrial quality players and is objectionable to audio/visual professionals.
Several attempts have been made in the prior art to synchronize still frame audio and visual presentations. Ramag, U.S. Pat. No. 3,878,560, is typical of the prior art approach. This patent addresses the use of a single audio/video source which allows play of a single video frame while audio continues. The audio signal is sampled at a rate compatible with the video source and stored on the same media as the video source. The audio is limited to 8.5 seconds per frame, and is embedded in the video media. As a result, mastering of the audio also requires mastering of the video since a single playback device delivers both signals. Further, the audio is of a fixed length per frame and limited in the number of output channels. Still further, this device, and other devices like it, do not use existing equipment for information retrieval, but requires non-conventional devices for both storage and display. As the audio has been sampled, it, therefore, has a limited band width.
Other devices, such as Omori, U.S. Pat. No. 3,909,512, are concerned with a method of transmission of sound when a still frame video signal is also transmitted. In Omori, the sound is digitized and frequency modulated into the transmitted signal. The received signal is buffered in digital memory and the time base expanded as it is converted back into analog form.
More recent devices are designed to provide enhanced video editing apparatus. Menezes, U.S. Pat. No. 4,394,745, disclosed several complex schemes for editing existing video tapes. The key to Menezes is a means of locating the position on the tape when a person already knows the locating key associated with that area of the tape. Further, Menezes concerns itself with combining video sources onto a single receiver.
Thus, it can be seen that there are drawbacks to the present methods of still frame audio/visual presentations and attempts to alleviate these drawbacks known in the art. There is a need in the art, therefore, for providing an audio/videodisc synchronizer that synchronizes audio and video signals from different sources. Further, there is a need for a synchronizer that enables long playing audio to be synchronized with still frame video displays. Still further, there is a need for a noncomplex, nonexpensive means for accomplishing these objectives with utilization of conventionally available devices. It, therefore, is an object of this invention to provide an audio/videodisc synchronizer that provides virtually unlimited audio per video frame; provides for remastering of the audio program independent of the video source; that eliminates the need for video frames with audio to be recorded on the videodisc in the same sequential order in which they will be replayed; and which allows for selection of a variety of video frames, for use in preparing new presentations, simply, quickly and easily.